Sometimes the issue is not on your end at all. During peak filing periods (quarterly deadlines), HMRC’s API servers experience heavy traffic. If the server response time exceeds the timeout limit set by the TaxCalc software, the connection drops. This "timeout" is frequently logged as Error Code 35.

Because HMRC requires strict digital links for MTD compliance, any break in that chain triggers an error code to protect the integrity of the data.

If you encounter this error, follow these troubleshooting steps in order, starting with the easiest fixes.

Corrupted cache can mimic Error 35.

If you have attempted all fixes above and Error 35 persists, professional support is needed. Before contacting TaxCalc (now part of the IRIS Software Group), gather:

Taxcalc Error Code 35 [upd] Jun 2026

Sometimes the issue is not on your end at all. During peak filing periods (quarterly deadlines), HMRC’s API servers experience heavy traffic. If the server response time exceeds the timeout limit set by the TaxCalc software, the connection drops. This "timeout" is frequently logged as Error Code 35.

Because HMRC requires strict digital links for MTD compliance, any break in that chain triggers an error code to protect the integrity of the data. taxcalc error code 35

If you encounter this error, follow these troubleshooting steps in order, starting with the easiest fixes. Sometimes the issue is not on your end at all

Corrupted cache can mimic Error 35.

If you have attempted all fixes above and Error 35 persists, professional support is needed. Before contacting TaxCalc (now part of the IRIS Software Group), gather: This "timeout" is frequently logged as Error Code 35