Several government agencies have released guidelines for late applications due to the US Emergency for COVID-19.  Links to these policies are provided here:

NIH

Coronavirus Disease 2019 (COVID-19): Information for NIH Applicants and Recipients of NIH funding
https://grants.nih.gov/grants/natural_disasters/corona-virus.htm

NIH LATE APPLICATION POLICY Due to Public Health Emergency for United States for 2019 Novel Coronavirus (COVID-19)
https://grants.nih.gov/grants/guide/notice-files/NOT-OD-20-082.html

General Frequently Asked Questions (FAQs) – Proposal Submission and Award Management Related to COVID-19:
https://grants.nih.gov/grants/guide/notice-files/NOT-OD-20-083.html

Flexibilities Available to Applicants and Recipients of Federal Financial Assistance Affected by COVID-19
https://grants.nih.gov/grants/guide/notice-files/NOT-OD-20-086.html

Guidance for NIH-funded Clinical Trials and Human Subjects Studies Affected by COVID-19
https://grants.nih.gov/grants/guide/notice-files/NOT-OD-20-087.html

Flexibilities for Assured Institutions for Activities of Institutional Animal Care and Use Committees (IACUCs) Due to COVID-19
https://grants.nih.gov/grants/guide/notice-files/NOT-OD-20-088.html

USDA

NIFA Deadline Extensions due to COVID-19
https://nifa.usda.gov/announcement/nifa-deadline-extensions-due-covid-19

NSF

Coronavirus Information
https://www.nsf.gov/news/special_reports/coronavirus/

Impact on Existing Deadline Dates
https://www.nsf.gov/bfa/dias/policy/covid19/covid19_deadlines.pdf

Frequently Asked Questions (FAQs) About the Coronavirus Disease 2019 (COVID-19) for National Science Foundation (NSF) Proposers and Awardees
https://www.nsf.gov/bfa/dias/policy/covid19/covid19faqs_proposerandawardee.pdf

Frequently Asked Questions (FAQs) About the Coronavirus Disease 2019 (COVID-19) for National Science Foundation (NSF) Panelists
https://www.nsf.gov/bfa/dias/policy/covid19/covid19faqs_panelists.pdf

Horizon 2020

As per the European Commission, all Horizon 2020 calls with deadlines between March 19th and April 15th have been extended. Please consult individual calls for proposals for specific details as they become available.