Separate by tax year and form type first
Do not mix 1099-NEC and 1099-MISC in the same Portal CSV, and do not mix tax years.
IRIS CSV batch planning
IRIS CSV 250-record limit: split batches without losing control
Publication 5717 (Rev. 9-2026) says each IRIS Taxpayer Portal CSV file may contain a maximum of 250 records, with one tax year and one form type per file. The safest split process preserves headers, row counts and source identifiers.
Step-by-step fix
Use a controlled troubleshooting sequence
Keep the IRS header in every batch
Each split file must remain a complete IRS-template CSV, including the unchanged header row.
Split at 250 records or fewer
The header does not count as a form record. Use predictable filenames such as 1099-NEC-2026-001.csv, -002.csv and so on.
Create a batch control total
Record source row count, file count, records per file and relevant dollar control totals before uploading.
Reconcile each IRS result
Tie every uploaded batch to its Receipt ID/status. Do not assume all batches succeeded because the first one did.
Common failure points
Problems that cause avoidable repeat filings
251 rows because the header was counted incorrectly
Publication 5717 says up to 250 forms per file, header row not included.
Header only in the first split file
Every file needs the valid IRS template header.
Different forms grouped together to fill a 250-record batch
Split by form type first. The Portal workflow only accepts one form type per CSV.
Duplicate rows across adjacent batches
Use stable source row IDs/account numbers and a deterministic split process, then reconcile counts before filing.
Quick answers
Frequently asked questions
Can I upload more than one CSV file?
Yes. Use as many valid batches as needed; reconcile each upload separately.
Can one CSV contain multiple issuers?
Publication 5717 states a file may contain multiple issuers when the Portal TCC role is a transmitter. Confirm your role and current guidance.
Does 1099ERICH split the files?
The software workflow is designed to create IRIS-ready CSV batches so larger imports can be prepared in controlled file sizes.
Need the next step?
Use the related 1099ERICH support or free tool before creating another IRS submission.
Open free CSV splitterBrowse Supported SoftwareOfficial sources
IRS resources used for this guide
Use the current agency source as the final authority when requirements change.
Prepare cleaner IRIS files before you upload.
1099ERICH imports Excel/CSV source data, validates supported records, prints recipient copies and creates IRIS-ready filing files on Windows.