Claude Sonnet 5 vs Qwen3.8 Flash

Same documents, same prompt: where each model is right, what it really costs and how fast it answers.

At a glance

Task · documents	English (US)	Czech	German	Spanish	French
Invoice extraction	99.8% / 82.4%	100.0% / 91.8%	99.0% / 93.5%	93.6% / 87.9%	98.7% / 90.6%
Email triage	98.2% / 97.5%	98.2% / 98.5%	97.9% / 97.9%	—	—
Personal data detection	99.7% / 99.2%	98.9% / 97.0%	99.7% / 99.6%	—	—
Contract clauses	100.0% / 95.1%	100.0% / 99.9%	98.2% / 98.0%	—	—

Correct fields: Claude Sonnet 5 / Qwen3.8 Flash; the better one in bold. Click a cell to see the details.

Invoice extraction · English (US) (150 documents)

Claude Sonnet 5 is more accurate by 17.5 pp. Qwen3.8 Flash is 7.7× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	99.8%	82.4%
Error-free documents	99%	57%
Per 1,000 documents	$8.84	$1.15
To fix / 1,000	13	427
Speed (median)	3.2 sec	17.4 sec
Valid answers	100.0%	90.7%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Supplier	100.0%	85.3%
Supplier ID (EIN, IČO…)	100.0%	88.7%
Invoice number	100.0%	85.3%
Payment reference	100.0%	79.3%
Invoice date	100.0%	85.3%
Due date	100.0%	85.3%
Net by tax rate	98.7%	70.0%
Tax by rate	99.3%	76.0%
Total	100.0%	85.3%
Currency	100.0%	84.0%
Bank account	100.0%	81.3%

Documents where they differ

Reid Office Products LLC · A-003849 · Scan · Claude Sonnet 5 11/11, Qwen3.8 Flash 0/11
Eagle Partners Co. · 4272 · Clean image · Claude Sonnet 5 11/11, Qwen3.8 Flash 0/11
Raleigh Engineering Inc. · INV253511 · Scan · Claude Sonnet 5 11/11, Qwen3.8 Flash 1/11
Hughes Janitorial Services Corp. · A-001911 · Scan · Claude Sonnet 5 11/11, Qwen3.8 Flash 1/11
Summit Services Inc. · INV-15230 · Scan · Claude Sonnet 5 11/11, Qwen3.8 Flash 2/11
Miranda-Vega Group LLC · 4959 · PDF text · Claude Sonnet 5 11/11, Qwen3.8 Flash 8/11
Liberty Systems Inc. · INV-17299 · PDF text · Claude Sonnet 5 11/11, Qwen3.8 Flash 9/11
Flores-Baker Group Co. · A-005694 · PDF text · Claude Sonnet 5 11/11, Qwen3.8 Flash 9/11

Invoice extraction · Czech (150 documents)

Claude Sonnet 5 is more accurate by 8.2 pp. Qwen3.8 Flash is 9.2× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	100.0%	91.8%
Error-free documents	100%	77%
Per 1,000 documents	$9.41	$1.02
To fix / 1,000	0	233
Speed (median)	3.6 sec	17.0 sec
Valid answers	100.0%	96.7%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Supplier	100.0%	93.3%
Supplier ID (EIN, IČO…)	100.0%	94.0%
VAT ID	100.0%	94.0%
Invoice number	100.0%	94.7%
Payment reference	100.0%	94.0%
Invoice date	100.0%	94.7%
Tax point	100.0%	94.7%
Due date	100.0%	94.7%
Net by tax rate	100.0%	80.0%
Tax by rate	100.0%	80.7%
Total	100.0%	94.0%
Currency	100.0%	94.0%
Bank account	100.0%	90.7%

Documents where they differ

Sedláček s.r.o. · 2025/0774 · Scan · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Sedlák s.r.o. · 20250158 · Photo · Claude Sonnet 5 13/13, Qwen3.8 Flash 9/13
Dvořák s.r.o. · FV2501487 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Hruška spol. s r.o. · 20250328 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Stavmet s.r.o. · 20250906 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Východočeská obchodní s.r.o. · FV2600186 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Mareš s.r.o. · FV2600300 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Elektrolog spol. s r.o. · 26700422 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13

Invoice extraction · German (150 documents)

Claude Sonnet 5 is more accurate by 5.5 pp. Qwen3.8 Flash is 9.3× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	99.0%	93.5%
Error-free documents	87%	87%
Per 1,000 documents	$10.42	$1.12
To fix / 1,000	133	127
Speed (median)	3.8 sec	19.0 sec
Valid answers	100.0%	94.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Supplier	100.0%	94.0%
Supplier ID (EIN, IČO…)	100.0%	94.0%
VAT ID	100.0%	94.0%
Invoice number	100.0%	92.7%
Payment reference	100.0%	88.7%
Invoice date	99.3%	94.0%
Tax point	100.0%	94.0%
Due date	100.0%	94.0%
Net by tax rate	89.3%	94.0%
Tax by rate	100.0%	94.0%
Total	100.0%	94.0%
Currency	100.0%	94.0%
Bank account	98.0%	94.0%

Documents where they differ

Bauunternehmung Schröder GmbH · 2026-0622 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Schreinerei Ferdi Schuster · 2025/0939 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Druckerei Baumann GmbH · 2025-0324 · Scan · Claude Sonnet 5 12/13, Qwen3.8 Flash 13/13
Hoffmann UG (haftungsbeschränkt) · 2025/1479 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Zimmermann & Schulz GmbH · RE11274 · Scan · Claude Sonnet 5 12/13, Qwen3.8 Flash 13/13
Dachdeckerei Fischer GmbH · 2025/0014 · Scan · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Braun IT-Service GmbH · RE2500825 · Photo · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Südform AG · 2025-0307 · PDF text · Claude Sonnet 5 12/13, Qwen3.8 Flash 13/13

Invoice extraction · Spanish (100 documents)

Claude Sonnet 5 is more accurate by 5.7 pp. Qwen3.8 Flash is 8.5× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	93.6%	87.9%
Error-free documents	77%	74%
Per 1,000 documents	$11.89	$1.40
To fix / 1,000	230	260
Speed (median)	4.0 sec	22.3 sec
Valid answers	95.0%	90.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Supplier	94.0%	86.0%
Supplier ID (EIN, IČO…)	95.0%	89.0%
VAT ID	95.0%	86.0%
Invoice number	95.0%	89.0%
Payment reference	94.0%	85.0%
Invoice date	95.0%	89.0%
Tax point	95.0%	87.0%
Due date	95.0%	89.0%
Net by tax rate	79.0%	86.0%
Tax by rate	95.0%	90.0%
Total	95.0%	89.0%
Currency	95.0%	89.0%
Bank account	95.0%	89.0%

Documents where they differ

Hermanos Peral S.L. · F2025-0581 · Scan · Claude Sonnet 5 0/13, Qwen3.8 Flash 13/13
Losa Comunicación S.L. · A-2026-0862 · PDF text · Claude Sonnet 5 0/13, Qwen3.8 Flash 13/13
Centro de Formación Mediterránea S.L. · 2026/0876 · Scan · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Aguirre Formación S.L. · 2025/0652 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Coloma Servicios Informáticos S.L.U. · PRO-2025-0066 · Scan · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Centro de Formación del Sur S.L. · F2026-0167 · PDF text · Claude Sonnet 5 0/13, Qwen3.8 Flash 13/13
Centro de Formación Centro S.L.U. · A-2025-1405 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Talleres Ibérica, S.A. · PF25/1188 · Clean image · Claude Sonnet 5 0/13, Qwen3.8 Flash 3/13

Invoice extraction · French (97 documents)

Claude Sonnet 5 is more accurate by 8 pp. Qwen3.8 Flash is 9× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	98.7%	90.6%
Error-free documents	96%	82%
Per 1,000 documents	$11.02	$1.23
To fix / 1,000	41	180
Speed (median)	4.4 sec	19.8 sec
Valid answers	99.0%	95.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Supplier	99.0%	91.0%
Supplier ID (EIN, IČO…)	99.0%	91.0%
VAT ID	99.0%	91.0%
Invoice number	99.0%	90.0%
Payment reference	97.9%	86.0%
Invoice date	99.0%	91.0%
Tax point	99.0%	92.0%
Due date	99.0%	89.0%
Net by tax rate	96.9%	91.0%
Tax by rate	99.0%	94.0%
Total	99.0%	91.0%
Currency	99.0%	91.0%
Bank account	97.9%	90.0%

Documents where they differ

Établissements Blanc SAS · F-11122 · Scan · Claude Sonnet 5 13/13, Qwen3.8 Flash 0/13
Guérin & Fils EURL · 2026-05-688 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 1/13
Nettoyage Mercier SASU · AC-10176 · Clean image · Claude Sonnet 5 13/13, Qwen3.8 Flash 3/13
Établissements Bertrand SASU · F2025-0066 · Scan · Claude Sonnet 5 11/13, Qwen3.8 Flash 12/13
Lefèvre & Fils SARL · FAC-2026-00198 · Photo · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Richard David EI · FAC25091009 · PDF text · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13

Email triage · English (US) (150 documents)

Claude Sonnet 5 is more accurate by 0.7 pp. Qwen3.8 Flash is 13.2× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	98.2%	97.5%
Error-free documents	84%	79%
Per 1,000 documents	$4.01	$0.30
To fix / 1,000	160	213
Speed (median)	3.8 sec	8.9 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Category	100.0%	100.0%
Priority	97.3%	97.3%
Sentiment	86.7%	80.7%
Customer name	100.0%	100.0%
Order number	100.0%	100.0%
Invoice number	100.0%	100.0%
Amount	100.0%	100.0%
Currency	100.0%	100.0%
Deadline	100.0%	99.3%

Documents where they differ

Angela Harmon · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 7/9
Jane Rubio · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9
Laurie Knight · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9
Sandra Hogan · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9
Joseph Jackson · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9

Email triage · Czech (150 documents)

Qwen3.8 Flash is more accurate by 0.4 pp. Qwen3.8 Flash is 11× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	98.2%	98.5%
Error-free documents	83%	87%
Per 1,000 documents	$4.91	$0.45
To fix / 1,000	167	133
Speed (median)	4.7 sec	13.0 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Category	100.0%	100.0%
Priority	96.0%	99.3%
Sentiment	87.3%	88.7%
Customer name	100.0%	99.3%
Order number	100.0%	99.3%
Invoice number	100.0%	100.0%
Amount	100.0%	100.0%
Currency	100.0%	100.0%
Deadline	100.0%	100.0%

Documents where they differ

Lucie Kašparová · Email · Claude Sonnet 5 8/9, Qwen3.8 Flash 9/9
Petra Šťastná · Email · Claude Sonnet 5 8/9, Qwen3.8 Flash 9/9
Václav Vítek · Email · Claude Sonnet 5 8/9, Qwen3.8 Flash 9/9
Milan Matějka · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9
Vanda Vacková · Email · Claude Sonnet 5 8/9, Qwen3.8 Flash 9/9
Růžena Sedláková · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9

Email triage · German (150 documents)

Both are equally accurate. Qwen3.8 Flash is 13.1× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	97.9%	97.9%
Error-free documents	81%	81%
Per 1,000 documents	$5.11	$0.39
To fix / 1,000	187	187
Speed (median)	4.3 sec	12.1 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Category	100.0%	100.0%
Priority	96.0%	96.0%
Sentiment	84.7%	84.7%
Customer name	100.0%	100.0%
Order number	100.0%	100.0%
Invoice number	100.0%	100.0%
Amount	100.0%	100.0%
Currency	100.0%	100.0%
Deadline	100.0%	100.0%

Documents where they differ

Rolf-Peter Metz · Email · Claude Sonnet 5 7/9, Qwen3.8 Flash 8/9
Linda Bähr · Email · Claude Sonnet 5 9/9, Qwen3.8 Flash 8/9
Augusta Lange · Email · Claude Sonnet 5 8/9, Qwen3.8 Flash 9/9

Personal data detection · English (US) (150 documents)

Claude Sonnet 5 is more accurate by 0.5 pp. Qwen3.8 Flash is 12.5× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	99.7%	99.2%
Error-free documents	98%	99%
Per 1,000 documents	$3.50	$0.28
To fix / 1,000	20	13
Speed (median)	2.5 sec	7.5 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Names	100.0%	99.3%
Email addresses	100.0%	99.3%
Phone numbers	100.0%	99.3%
Addresses	98.0%	98.7%
Dates of birth	100.0%	99.3%
National IDs	100.0%	99.3%
Bank accounts	100.0%	99.3%

Documents where they differ

Both models got the same number of fields right on every example document.

Personal data detection · Czech (150 documents)

Claude Sonnet 5 is more accurate by 1.9 pp. Qwen3.8 Flash is 10× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	98.9%	97.0%
Error-free documents	92%	89%
Per 1,000 documents	$4.06	$0.41
To fix / 1,000	80	113
Speed (median)	3.2 sec	9.6 sec
Valid answers	100.0%	99.3%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Names	96.7%	90.7%
Email addresses	100.0%	98.0%
Phone numbers	100.0%	97.3%
Addresses	97.3%	96.7%
Dates of birth	98.0%	98.0%
National IDs	100.0%	99.3%
Bank accounts	100.0%	98.7%

Documents where they differ

Růžena Tichá · Text · Claude Sonnet 5 6/7, Qwen3.8 Flash 7/7
Jonáš Toman · Text · Claude Sonnet 5 6/7, Qwen3.8 Flash 7/7
Rudolf Konečný · Text · Claude Sonnet 5 6/7, Qwen3.8 Flash 7/7
Zikmund Sedláček · Text · Claude Sonnet 5 6/7, Qwen3.8 Flash 7/7
Naděžda Žáková · Text · Claude Sonnet 5 7/7, Qwen3.8 Flash 6/7

Personal data detection · German (150 documents)

Claude Sonnet 5 is more accurate by 0.1 pp. Qwen3.8 Flash is 12.3× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	99.7%	99.6%
Error-free documents	98%	99%
Per 1,000 documents	$4.40	$0.36
To fix / 1,000	20	7
Speed (median)	3.7 sec	12.2 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Names	98.7%	99.3%
Email addresses	100.0%	99.3%
Phone numbers	100.0%	99.3%
Addresses	100.0%	99.3%
Dates of birth	99.3%	100.0%
National IDs	100.0%	100.0%
Bank accounts	100.0%	100.0%

Documents where they differ

Both models got the same number of fields right on every example document.

Contract clauses · English (US) (150 documents)

Claude Sonnet 5 is more accurate by 4.9 pp. Qwen3.8 Flash is 8.1× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	100.0%	95.1%
Error-free documents	100%	69%
Per 1,000 documents	$5.04	$0.62
To fix / 1,000	0	307
Speed (median)	3.4 sec	14.1 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Provider	100.0%	69.3%
Provider ID	100.0%	100.0%
Client	100.0%	69.3%
Client ID	100.0%	100.0%
Contract type	100.0%	100.0%
Price (net)	100.0%	100.0%
Currency	100.0%	100.0%
Billing period	100.0%	100.0%
Effective date	100.0%	99.3%
End date	100.0%	100.0%
Notice period (months)	100.0%	100.0%
Late-payment penalty (% per day)	100.0%	99.3%
Governing law	100.0%	99.3%

Documents where they differ

Page Printing LLC · Raleigh Printing Inc. · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 9/13
Santiago-Harris Group Co. · Columbus Printing Inc. · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Pittsburgh Construction Co. · Evans Electric LLC · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Frye & Sons, Co. · Nunez-Smith Group Inc. · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Kim Electric Co. · Ramos & Sons, Co. · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Blue Ridge Services Corp. · Bishop-Kim Group LLC · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
White Landscaping Co. · Douglas-Ali Group LLC · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13
Rose & Sons, Inc. · Eagle Systems Inc. · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 11/13

Contract clauses · Czech (150 documents)

Claude Sonnet 5 is more accurate by 0.1 pp. Qwen3.8 Flash is 9.6× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	100.0%	99.9%
Error-free documents	100%	99%
Per 1,000 documents	$6.05	$0.63
To fix / 1,000	0	13
Speed (median)	3.6 sec	13.6 sec
Valid answers	100.0%	100.0%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Provider	100.0%	100.0%
Provider ID	100.0%	100.0%
Client	100.0%	100.0%
Client ID	100.0%	100.0%
Contract type	100.0%	98.7%
Price (net)	100.0%	100.0%
Currency	100.0%	100.0%
Billing period	100.0%	100.0%
Effective date	100.0%	100.0%
End date	100.0%	100.0%
Notice period (months)	100.0%	100.0%
Late-payment penalty (% per day)	100.0%	100.0%
Governing law	100.0%	100.0%

Documents where they differ

Interservis s.r.o. · Staněk s.r.o. · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13

Contract clauses · German (150 documents)

Claude Sonnet 5 is more accurate by 0.2 pp. Qwen3.8 Flash is 9.1× cheaper.

Metric	Claude Sonnet 5	Qwen3.8 Flash
Correct fields	98.2%	98.0%
Error-free documents	87%	87%
Per 1,000 documents	$7.11	$0.78
To fix / 1,000	133	127
Speed (median)	4.3 sec	19.7 sec
Valid answers	100.0%	99.3%

Accuracy per field

Field	Claude Sonnet 5	Qwen3.8 Flash
Provider	100.0%	99.3%
Provider ID	87.3%	94.7%
Client	100.0%	99.3%
Client ID	89.3%	94.7%
Contract type	100.0%	99.3%
Price (net)	100.0%	99.3%
Currency	100.0%	99.3%
Billing period	100.0%	99.3%
Effective date	100.0%	99.3%
End date	100.0%	99.3%
Notice period (months)	100.0%	99.3%
Late-payment penalty (% per day)	100.0%	99.3%
Governing law	100.0%	91.3%

Documents where they differ

Hansawerk GmbH · Schreinerei Weber AG · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 10/13
Meyer AG · Hartmann GmbH · Contract text · Claude Sonnet 5 11/13, Qwen3.8 Flash 13/13
Hahn & Schulz GmbH & Co. KG · Alpentec GmbH · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Maintec GmbH · Schreinerei Wagner GmbH · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Kraus Consulting GmbH · Lange Consulting GmbH & Co. KG · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13
Schulz Systemtechnik GmbH · Elbdata GmbH · Contract text · Claude Sonnet 5 11/13, Qwen3.8 Flash 12/13
Richter & Albrecht e.K. · Elbmetall UG (haftungsbeschränkt) · Contract text · Claude Sonnet 5 11/13, Qwen3.8 Flash 12/13
Keller & Köhler UG (haftungsbeschränkt) · Hansalogistik GmbH · Contract text · Claude Sonnet 5 13/13, Qwen3.8 Flash 12/13